Variation in Nutrient Content of Loblolly Pine Needles with Season, Age, Soil, and Position on the Crown

Abstract

AbstractThe nutrient content for the 17‐month cycle of loblolly pine (Pinus taeda) needles from the upper, middle, and bottom parts of the crown was determined for the first growth whorl of 1959. Needle weight per fascicle increased until April 1960 and then decreased slowly until abscission. Percentages of N, Ca, and Mg were greater in the needles from the bottom part of the crown, whereas P and K percentages were greater in the upper part of the crown. Percentage of N in the needles increased during winter months after the first growing season. Phosphorus percentage decreased each month for 1 year and then increased slightly. Calcium and Mg percentages in general increased throughout the growth and maturation of the needles with the content approaching a constant value during winter months. The basic influence of the soil on some plots was reflected in a two‐fold difference in Ca and a three‐fold difference in Mg content of the mature needles. It appears that about one‐half of the N, P, and K are translocated from the needles immediately before abscission.The results of this study indicate that needles of the first growth whorl of the season at the top of the crown should be sampled in August and September of the first growing season for P; from December through March for K, Ca, and Mg; and from June through September of the second growing season for N.